The “reversible addition fragmentation chain transfer” (RAFT) process is a promising method of conducting controlled free-radical polymerizations.
The structural attachment of the polymer to the surface can be controlled via the choice and the chemical structure of what are called the RAFT agents, as described inter alia in DE 69808622 T3.
In the case of controlled free-radical polymerization too, the RAFT agents known in the prior art give rise to polymers which, after being mixed into a rubber mixture, especially a sulfur-crosslinkable rubber mixture for motor vehicle tires, cords, belts, or hoses, and after vulcanization (sulfur crosslinking), have a multitude of free chain ends (“dangling ends”). The greater the number of free chain ends, the greater the energy loss and hence the build-up of heat in the rubber mixture, since the free polymer chain ends are particularly mobile and convert energy to kinetic energy. The rubber mixture therefore has an energy-damping effect, which has an adverse effect on rolling resistance when used, for example, in motor vehicle tires.